A Formal Architectural Description Language based on Symbolic Transition Systems and Modal Logic

International audienceComponent Based Software Engineering has now emerged as a discipline for system development. After years of battle between component platforms, the need for means to abstract away from specific implementation details is now recognized. This paves the way for model driven approaches (such as MDE) but also for the more older Architectural Description Language (ADL) paradigm. In this paper we present KADL, an ADL based on the Korrigan formal language which supports the following features: integration of fully formal behaviours and data types, expressive component composition mechanisms through the use of modal logic, specification readability through graphical notations, and dedicated architectural analysis techniques. Key Words: Architectural Description Language, Component Based Software Engineering, Mixed Formal Specifications, Symbolic Transition Systems, Abstract Data Types, Modal Logic Glue, Graphical Notations, Verification

Independent verification of specification models for large software systems at the early phases of development lifecycle

One of the major challenges facing the software industry, in general and IV&V (Independent Verification and Validation) analysts in particular, is to find ways for analyzing dynamic behavior of requirement specifications of large software systems early in the development lifecycle. Such analysis can significantly improve the performance and reliability of the developed systems. This dissertation addresses the problem of developing an IV&V framework for extracting semantics of dynamic behavior from requirement specifications based on: (1) SART (Structured Analysis with Realtime) models, and (2) UML (Unified Modeling Language) models.;For SART, the framework presented here shows a direct mapping from SART specification models to CPN (Colored Petrinets) models. The semantics of the SART hierarchy at the individual levels are preserved in the mapping. This makes it easy for the analyst to perform the analysis and trace back to the corresponding SART model. CPN was selected because it supports rigorous dynamic analysis. A large scale case study based on a component of NASA EOS system was performed for a proof of the concept.;For UML specifications, an approach based on metamodels is presented. A special type of metamodel, called dynamic metamodel (DMM), is introduced. This approach holds several advantages over the direct mapping of UML to CPN. The mapping rules for generating DMM are not CPN specific, hence they would not change if a language other than CPN is used. Also it makes it more flexible to develop DMM because other types of models can be added to the existing UML models. A simple example of a pacemaker is used to illustrate the concepts of DMM

Semantics and Verification of UML Activity Diagrams for Workflow Modelling

This thesis defines a formal semantics for UML activity diagrams that is suitable for workflow modelling. The semantics allows verification of functional requirements using model checking. Since a workflow specification prescribes how a workflow system behaves, the semantics is defined and motivated in terms of workflow systems. As workflow systems are reactive and coordinate activities, the defined semantics reflects these aspects. In fact, two formal semantics are defined, which are completely different. Both semantics are defined directly in terms of activity diagrams and not by a mapping of activity diagrams to some existing formal notation. The requirements-level semantics, based on the Statemate semantics of statecharts, assumes that workflow systems are infinitely fast w.r.t. their environment and react immediately to input events (this assumption is called the perfect synchrony hypothesis). The implementation-level semantics, based on the UML semantics of statecharts, does not make this assumption. Due to the perfect synchrony hypothesis, the requirements-level semantics is unrealistic, but easy to use for verification. On the other hand, the implementation-level semantics is realistic, but difficult to use for verification. A class of activity diagrams and a class of functional requirements is identified for which the outcome of the verification does not depend upon the particular semantics being used, i.e., both semantics give the same result. For such activity diagrams and such functional requirements, the requirements-level semantics is as realistic as the implementation-level semantics, even though the requirements-level semantics makes the perfect synchrony hypothesis. The requirements-level semantics has been implemented in a verification tool. The tool interfaces with a model checker by translating an activity diagram into an input for a model checker according to the requirements-level semantics. The model checker checks the desired functional requirement against the input model. If the model checker returns a counterexample, the tool translates this counterexample back into the activity diagram by highlighting a path corresponding to the counterexample. The tool supports verification of workflow models that have event-driven behaviour, data, real time, and loops. Only model checkers supporting strong fairness model checking turn out to be useful. The feasibility of the approach is demonstrated by using the tool to verify some real-life workflow models

Applying the Engineering Statechart Formalism to the evaluation of soft real-time in operating systems : a use case tailored modeling and analysis technique

Multimedia applications that have emerged in recent years impose unique requirements on an underlying general purpose operating system (GPOS). The suitability of a GPOS for multimedia processing is judged by its soft real-time capabilities. To date, the question of how these capabilities can be assessed has scarcely been addressed: this is a gap in GPOS research. By answering questions on the impacts of the Interrupt Handling Facility (IHF) on the overall soft real-time capabilities of a GPOS, this thesis contributes to the filling of this blank space. The Engineering Statechart Formalism (ESF), a use case tailored formal method of modeling real-world OS, is syntactically and semantically defined. Models of the IHF of selected real-world operating systems are then created by means of this technique. As no appropriate real-time concept fitting the goals of this thesis as yet exists, a suitable definition is constructed. By projecting this system-wide idea to the interrupt subsystem, specific indicators for this subsystem are erived. These indicators are then evaluated by applying formal techniques such as graph-based analysis and temporal logic model checking to the ESF models. Finally, the assertions derived from this evaluation are interpreted with respect to their impacts on real-time multimedia processing in different general purpose operating systems.Multimedia-Anwendungen haben in den letzten Jahren weite Verbreitung erfahren. Solche Anwendungen stellen besondere Anforderungen an das Betriebssystem (BS), auf dem sie ausgeführt werden. Insbesondere Echtzeitfähigkeiten des Betriebssystems sind von Bedeutung, wenn es um seine Eignung für Multimedia-Verarbeitung geht. Bis heute wurde die Frage, wie sich diese Fähigkeiten konkret innerhalb eines BS manifestieren, nur unzureichend untersucht. Die vorliegende Arbeit leistet einen Beitrag zur Füllung dieser Lücke in der BS-Forschung. Die Effekte des Subsystems zur Unterbrechungsbehandlung in BS auf die Echtzeitfähigkeit des Gesamtsystems werden detailliert auf Basis von Modellen dieses Subsystems in verschiedenen BS analysiert. Um eine formale Auswertung zu erlauben, wird eine auf den Anwendungsfall zugeschnittene formale Methode zur BS-Modellierung verwendet. Die spezifizierte Syntax und Semantik dieses Engineering Statechart Formalism (ESF) basieren auf dem klassischen Statechart-Formalismus. Da bislang kein geeigneter Echtzeit-Begriff existiert, wird eine konsistente Definition hergeleitet. Durch die Abbildung dieser sich auf das Gesamtsystem beziehenden Eigenschaft auf die Unterbrechungsbehandlung werden spezifische Indikatoren für dieses Subsystem hergeleitet. Die Ausprägungen dieser Indikatoren für die verschiedenen untersuchten Betriebssyteme werden anhand formaler Methoden wie graphbasierter Analyse und Temporal Logic Model Checking ausgewertet. Die Interpretation der Untersuchungsergebnisse liefert Aussagen über die Effekte der Implementierung der Unterbrechungsbehandlung auf die Echtzeitfähigkeit der untersuchten Betriebssysteme bei der Verarbeitung von multimedialen Daten

Using formal methods to support testing

Formal methods and testing are two important approaches that assist in the development of high quality software. While traditionally these approaches have been seen as rivals, in recent years a new consensus has developed in which they are seen as complementary. This article reviews the state of the art regarding ways in which the presence of a formal specification can be used to assist testing

Developing Specifications by using Operators: a Process to guarantee correctness by construction

We propose a process model for the development of specifications based on the notions of multi-view state and of operators. A specification state consists of a UML view and a B expression of the same specification. Operators model design decisions as the simultaneous transformation of UML and B descriptions. A specification development is a sequence of applications of operators. We define a notion of coherence of a specification state which allows us to define formally a notion of correctness for operators. Thus, the development process guarantees that the specification can be safely verified and validated

Modeling Time in Computing: A Taxonomy and a Comparative Survey

The increasing relevance of areas such as real-time and embedded systems, pervasive computing, hybrid systems control, and biological and social systems modeling is bringing a growing attention to the temporal aspects of computing, not only in the computer science domain, but also in more traditional fields of engineering. This article surveys various approaches to the formal modeling and analysis of the temporal features of computer-based systems, with a level of detail that is suitable also for non-specialists. In doing so, it provides a unifying framework, rather than just a comprehensive list of formalisms. The paper first lays out some key dimensions along which the various formalisms can be evaluated and compared. Then, a significant sample of formalisms for time modeling in computing are presented and discussed according to these dimensions. The adopted perspective is, to some extent, historical, going from "traditional" models and formalisms to more modern ones.Comment: More typos fixe